However, just prior to the announcement I received some information pointing to a move away from the ARM Cortex A9 used in the A5. Given Apple's reliance on fully licensed ARM cores in the past, the expected performance gains and unpublishable information that started all of this I concluded Apple's A6 SoC likely featured two ARM Cortex A15 cores.
It turns out I was wrong. But pleasantly surprised.
The A6 is the first Apple SoC to use its own ARMv7 based processor design. The CPU core(s) aren't based on a vanilla A9 or A15 design from ARM IP, but instead are something of Apple's own creation.
So this is the first Apple core we’ve seen done with custom digital layout. In fact, with the exception of Intel CPUs, it’s one of the first custom laid out digital cores we’ve seen in years! This must have taken a large team of layout engineers quite a long time. The obvious question is, why? This is a more expensive and time-consuming method of layout. However it usually results in a faster maximum clock rate, and sometimes results in higher density. Certainly one possibility is that Apple could not meet timing on a automatically laid out block, and chose to go with a custom laid out block. Was this a decision at the architecture stage, or did timing fail late in the design cycle and a SWAT team of layout engineers brought in to save the day? We’ll probably never know, but it is fascinating, and also 2X faster (according to the below image)